1. Field of the Invention
The invention presented herein relates to a signal discriminator circuit for providing a control signal only in response to a consecutive predetermined number of input signals presented at a predetermined frequency, the signal discriminator circuit being particularly useful in a remote control system for a traffic signal control system which provides remote control in response to either of at least two possible signals with the response to one of the signals providing priority control of the traffic signal control system.
2. Description of the Prior Art
Traffic signal remote control systems are currently in use which utilize an optical energy emitter that is mounted on a selected vehicle, such as a police vehicle or ambulance, for the transmission of optical energy pulses that occur at regular intervals and are directed toward an intersection as the vehicle approaches the intersection. The optical transmissions are detected by a directional optical detector that is mounted in the vicinity of the intersection. The detected signal is applied to a signal recognition or discriminator circuit which produces a control signal at its output if the detected signal satisfies the qualifications imposed on the input signal by the discriminator circuit. The output signal from the discriminator is applied to the controller of the traffic signal control system via appropriate circuitry connected to the controller to cause a green light to be presented at the traffic light face for the optical signal transmitting vehicle allowing it to pass through an intersection in a normal manner.
It is desirable that a traffic signal remote control system be provided wherein remote control of the traffic signal control system is carried out on a multiple priority basis. For example, if a vehicle, designated as a low priority vehicle, were to approach an intersection and emit a light energy signal for causing the traffic light controller to provide a green light to the vehicle and, subsequently, a vehicle, designated as a high priority vehicle, were to approach the intersection on a conflicting path, it would be desirable that an optical energy signal transmitted from the high priority vehicle would cause the system to over-ride the action initiated by the low priority vehicle to cause a green light to be provided to the high priority vehicle permitting it to pass through the intersection before the low priority vehicle.
The desired multiple priority remote control system is attained by the use of the signal discriminator circuit in accordance with the present invention which provides a control signal from pulses obtained from optical energy signals of only a particular repetition frequency and excludes other optical energy signals that may be detected by the optical detector.